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January 2014

The following properties a cotton fibre should have to contain of:-
1. Fibre Fineness: 
Fineness is one of the most important parameter determining the yarn quality. This is the best cotton properties that almost all of the cotton importers wants. Cotton  Fibre fineness influences the number of fibre in cross section. The finer fibre results the higher no. of fibre in yarn cross-sections. Fibre fineness influences primarily-
A) Spinning limit. B) Lustre. C) Yarn Strength. D) Handle E) Yarn Evenness F) Productivity.
2. Maturity: 
The maturity of cotton fibre defines in terms of the development of the cell wall. A fully mature fibre has a developed cell wall. On the other hand, an immature fibre has a very thin cell wall. A fibre is to be considered as mature fibre when the cell wall of moisture swollen fibre represents 50% to 80% of the round cross section, as immature fibre represents 30% to 45% and as dead when it represents less than 25%.
Immature fibres lead to –a) napping b) loss of yarn strength c) high proportion of short fibre d) varying dyeability. So good cotton properties is to said as matured cotton fibre.
3. Fibre Length: 
The average length of spinnable fibre is called staple length. Staple length is one of the most important fibre characteristics. The quality, count, strength, etc depend on the staple length of the fibre. Higher the staple length, higher the yarn quality. Staple length influences –a) yarn evenness b) lustre of the product c) spinning limit d) yarn strength e) yarn hairiness f) handle of the product
The following length grouping are currently used in stating the trade staple or basic cotton properties-
  • Short Staple: 1″ or less.
  • Medium Staple: 1 and 1/32 inch to 1 and 1/8 inch
  • Long Staple: 1 and 5/32 inch to 1 and 3/8 inch.
  • Extra Long Staple: 1 and 13/32 inch and above.

4.  Cotton Fibre Strength: 
Toughness of fiber has a direct effect on yarn and fabric strength.  Cotton Properties means such type of physical behavior of a fibre. The higher the fibre strength, the higher the yarn and fabric strength. Very weak cotton tends to rupture during processing both in blow room and carding, creating short fibres and consequently deteriorate yarn strength and uniformity. Some significant breaking strength of fibres are-
  • Polyester >>35 to 60 CN/Tex
  • Cotton>>>>15 to 40 CN/Tex
  • Wool>>>>12 to 18 CN/Tex

5.  Cotton Fibre Cleanness:
 In addition to usable fibre, cotton stocks contain various kinds of foreign matters. Some vegetable matters are- a) husk portion, b) seed portion c) stem portion d) leaf portion e) wood portion.
  • Some mineral matters are- a) earth b) sand c) dust.
  • Some other foreign materials are- a) metal fragments b) cloth fragments c) packing materials.

6. Cotton Fibre Elongation: 
Elongation is specified as a percentage of the starting length. Textile products without classify would hardly be usable. They must be deformed and also return to the original shape. The fibre elongation should be at least 1 to 2%. The greater crease resistance of wool compared with cotton arises due to difference in theirelongation.

Introduction
Spandex, Lycra or elastane is a synthetic fibre known for its exceptional elasticity. It is made up of a long chain polymer called polyurethane, which is produced by reacting polyester with a di isocyanate. Spandex gained interest quickly due to its superiority to the strength in durability of rubber. Spandex also has a better resistance to dry heat & oil, in comparison to rubber. The level of comfort and wicking ability found in Spandex are unparalleled, and do not exist in such high amount with any other fabric. Spandex is being used in a continually widening array of clothing articles, including woven and knits, and synthetics and natural fibers.

Raw Materials
A variety of raw materials are used to produce stretchable spandex fibers. This includes prepolymers which produce the backbone of the fiber, stabilizers which protect the integrity of the polymer, and colorants.
Two types of prepolymers are reacted to produce the spandex fiber polymer back-bone. One is a flexible macroglycol while the other is a stiff diisocyanate. The macro-glycol can be Polyester, polyether, polycarbonate, polycaprolactone or some combination of these. These are long chain polymers, which have hydroxyl groups (-OH) on both ends. The important feature of these molecules is that they are long and flexible. This part of the spandex fiber is responsible for its stretching characteristic. The other prepolymer used to produce spandex is a polymeric diisocyanate. This is a shorter chain polymer, which has an isocyanate (-NCO) group on both ends. The principal characteristic of this molecule is its rigidity. In the fiber, this molecule provides strength.
Basic Principles of Spandex Fiber Production
The polymer chain is a segmented block copolymer containing long, randomly coiled, liquid, soft segments that move to a more linear, lower entropy, structure. The hard segments act as “virtual cross-links” that tie all the polymer chains together into an infinite network. This network prevents the polymer chains from slipping past each other and taking on a permanent set or draw. When the stretching force is removed, the linear, low entropy, soft segments move back to the preferred randomly coiled, higher entropy state, causing the fiber to recover to its original shape and length. This segmented block copolymer is formed in a multi-step proprietary process. It is extruded into a fiber as a monofilament threadline or for most products into a multiplicity of fine filaments that are coalesced shortly after they are formed into a single threadline.

The Manufacturing Process
Spandex fibers are produced in four different ways including melt extrusion, reaction spinning, solution dry spinning, and solution wet spinning. Each of these methods involves the initial step of reacting monomers to produce a prepolymer. Then the prepolymer is reacted further, in various ways, and drawn out to produce a long fiber. Since solution dry spinning is used to produce over 90% of the world's spandex fibers, it is described.




      A.   Polymer reactions
1. The first step in the production of spandex is the production of the prepolymer. This is done by mixing a macroglycol with a diisocyanate monomer. The compounds are mixed in a reaction vessel and under the right conditions they react to form a prepolymer. Since the ratio of the component materials produces fibers with varying characteristics, it is strictly controlled. A typical ratio of glycol to diisocyanate may be 1:2.
2. In dry spinning fiber production, the prepolymer is further reacted with an equal amount of diamine. This is known as a chain extension reaction. The resulting solution is diluted with a solvent to produce the spinning solution. The solvent helps make the solution thinner and more easily handled. It can then be pumped into the fiber production cell.
      B.   Producing the fibers
3. The spinning solution is pumped into a cylindrical spinning cell where it is cured and converted into fibers. In this cell, the polymer solution is forced through a metal plate, called a spinneret, which has small holes throughout. This causes the solution to be aligned in strands of liquid polymer. As the strands pass through the cell, they are heated in the presence of a nitrogen and solvent gas. These conditions cause the liquid polymer to chemically react and form solid strands.
4. As the fibers exit the cell, a specific amount of the solid strands are bundled together to produce the desired thickness. This is done with a compressed air device that twists the fibers together. In reality, each fiber of spandex is made up of many smaller individual fibers that adhere to one another due to the natural stickiness of their surface.

       C.   Final processing
 5. The fibers are then treated with a finishing agent. This may be magnesium stearate another polymer such as poly (dimethyl-siloxane). These finishing materials prevent the fibers from sticking together and aid in textile manufacture. After this treatment, the fibers are transferred through a series of rollers onto a spool. The windup speed of the entire process can be anywhere from 300-500 mi (482.7-804.5 km) per minute depending on the thickness of the fibers.

6 .When the spools are filled with fiber, they are put into final packaging and shipped to textile manufacturers and other customers. Here, the fibers may be woven with other fibers such as cotton or nylon to produce the fabric that is used in clothing manufacture. This fabric can also be dyed to produce a desired color.

SPANDEX FIBER CHARACTERISTICS
·         Can be stretched repeatedly and still recover to very near its original length and shape
·         Generally, can be stretched more than 500% without breaking
·         Stronger, more durable and higher retractive force than rubber
·         Lightweight, soft, smooth, supple
·         In garments, provides a combination of comfort and fit, prevents bagging and sagging
·         Heat-settable — facilitates transforming puckered fabrics into flat fabrics, or flat fabrics into permanent rounded shapes
·         Dyeable
·         Resistant to deterioration by body oils, perspiration, lotions or detergents
·         Abrasion resistant
·         When fabrics containing spandex are sewn, the needle causes little or no damage from “needle cutting” compared to the older types of elastic materials
·         Available in fiber diameters ranging from 10 denier to 2500 denier
·         Available in clear and opaque lusters 
PHYSICAL PROPERTIES:-

1. Cross section- spandex filaments are extruded usually from circular orifices, but the evaporation of solvent or the effects of drying may produce non-circular cross-sectional shapes. This may take various forms. In the multi-filament yarns, individual filaments are often fused together in places. The number of filaments in a yarn may be as few as 12 or as many as 50; the linear density of filaments ranges from 0.1 to 3 Tex (g/km).

2. Density: The density of spandex filaments ranges from 1.15 to 1.32 g/cc, the fibres lower density being based on polyesters.

3. Moisture regain: The moisture of fibres from which the surface finish has been removed lies between 0.8 & 1.2%

4. Length: It can be of any length. May be used as filament or staple fibre

5. Color: It has white or nearly white color.

6. Luster:-It has usually dull luster.
7. Strength: Low strength compared to most other synthetic fiber.

8. Elasticity: Elastic properties are excellent. This is the outstanding characteristic of the fibre.

9. Heat: The heat resistance varies considerably amongst the different degrades over 300 F.

10: Flammability: It Burn slowly.

11: Electrical Conductivity: It has Low electrical conductivity.
12. Breaking Tenacity: 0.6 to 0.9grams/denier.

CHEMICAL PROPERTIES.

1. Acid:Good resistance to most of acids unless exposure is over 24 hours.

2. Alkalies: Good resistance to most of the alkalies, but some types of alkalies may damage the   fibre.

3. Organic solvents: offer resistance to dry cleaning solvents.

4. Bleaches: can be degraded by sodium hypo chloride. Chlorine bleach should not be used.

5. Dyeing: A full range of colures is available. Some types are more difficult to dye than others.

Characteristics:Lightweight Can be stretched over 500% without breaking Able to be stretched repetitively and still recover original length Abrasion resistant Stronger, more durable than rubber Soft, smooth and supple Resistant to body oils, perspiration, lotions or detergents No static or pilling problems

Major End Uses: Apparel - articles where stretch is desired: athletic apparel, bathing suits, foundation garments, ski pants, slacks, hosiery, socks, belts.

MAJOR SPANDEX FIBRE USES

·         Apparel and clothing articles where stretch is desired, generally for comfort and fit, such as: athletic, aerobic, and exercise apparel, belts, competitive swimwear, dance belts worn by male ballet dancers and others, gloves, hosiery, leggings, netball bodysuits, orthopedics brace, ski pants, skinny jeans, slacks, miniskirts, socks, swimsuits/bathing suits, innererwear, wetsuits
·         Compression garments such as: cycling shorts, foundation garments, motion capture suits, rowing unisuit
·         Shaped garmentssuch as support hose, surgical hose, superhero, women's volleyball shorts, wrestling singlet
·         Home furnishings, such as micro bead pillows




INTRODUCTION
Lyocell is a man-made cellulosic fiber. It is produced by solvent spinning, i.e., regenerating into fiber form out of a cellulose solution in an organic solvent. It is made up of cellulose and derived from plant sources like wood pulp. For the solution spinning of lyocell fiber the wood pulp is first dissolved at 90 to 1200 C in a solvent NMMO (N-methyl morpholine N- oxide) under normal pressure to form viscose solution. The solution thus obtained is then filtered and extruded by means of fine jet into a water bath; here the regeneration of cellulose takes place resulting in the formation of fiber. The cellulose is regenerated after passing through an air gap into spinning bath. Finally, the fiber is drawn off with appropriate stretching followed by washing, drying and winding of the fiber. With the higher spinning speeds it is possible to produce fine deniers.
(NOTE: The manufacturing of Lyocell is same as that of viscos only difference is that NO AGEING, NO XANTHATION, NO USE OF CS2 instead using N-methyl morpholine N- oxide)

SOLVENT SPUN TECHNOLOGY:
  • Product is Lyocell (Third generation Cellulosic fibre)
  • This production process is also known as solvent spun technology.
  • When the solvent comes in contact with water, water is evaporated by means of heat and solvent is extracted. This is neutralized with the help of absorption chillers.
  • Thus the process remains eco as well as environment friendly.
  • During manufacturing of third generation man made Cellulosic fibre (Lyocell fibre) there are absolutely zero discharges to atmosphere and thus there is absolutely zero pollution of atmosphere. Moreover water used for producing unit kg of fibre is significantly lesser when compared to water used for producing first and second generation man made Cellulosic fibres.

PROPERTIES OF LYOCELL/TENCEL

1.    cross section- circular
2.    It is the strongest of all the cellulosic fibers.
3.    Tenacity lies in the range of 38-42 cN/Tex.
4.    It has a reduction of 15% of wet strength ie retain 85% of their strength when wet and hence gives an edge over the others.
5.    It is highly oriented and crystalline in nature,The ratio of crystalline to amorphous area is approximately around 9:1.
6.    They are soft and lustrous with Smooth and uniform surface.
7.    They show good drape and fluidity.
8.    They are highly stable at high temperature. It does not melt but starts loosing strength rapidly at 300 0C and finally gets ignited at 420 0C
9.    Tencel is inert to most of the organic solvents.
10.However, it degrades in the presence of hot dilute or cold concentrated mineral acid.
11.Alkalies causes swelling at first (max. at 9% NaOH solution, 250C) and then ultimately disintegration
12.Under certain conditions lyocell fibres fibrillate which enables fabrics to be developed with interesting aesthetics.

END USES OF LYOCELL/TENCEL

Lyocell is more expensive to producethan cotton or rayon. It is used in many everyday fabrics.
·         Staple fibres are used in clothes such as denim, chino, underwear, casual wear, and towels.
·         Filament fibersare used in items that have a silkier appearance such as women’s clothing and men’s dress shirts
·          Lyocell can be blended with a variety of other fibers such as silk, cotton, rayon, polyester, linen, nylon, and wool. Lyocell is also used in conveyor belts, specialty papers and medical dressings.
·         Tencel is also used for making some brands of baby diaper wipe.
·         Lyocell fibres are mostly used for apparel fabrics, especially outerwear, but it has been shown that, due to the fibrillating property some very interesting nonwoven fabrics can be made as well.

PRODUCERS
Lyocell is manufactured by Lenzing AG in Mobile, Alabama, USA, in Grimsby, England, and in Heiligenkreuz, Burgenland, Austria.

Ashish Hulle

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